The macrons are for length, not stress. Normal stress in Imperial Sinemi is root-final. The repetition of the same notes is supposed to be for the purpose of entering an altered state. Kind of a meditative thing? It's not uncommon to hear a Sinemi humming the tune while focused on some task. It's also used to calm oneself down. Having a common cultural practice for such is very useful in a world where heightened emotions can rip open holes in the fabric of reality, letting loose the wild energies of the spirit world.